A first-ever duel between the two Grand Slam champions with diametrically opposed playing styles ultimately boiled down to a simple mathematical formula.

Young firebrand Ostapenko’s 30 winners far outweighed the 10 struck by the wily Kerber but the 36 unforced errors she committed on Centre Court made for an ugly balance sheet.

The 30-year-old Kerber, who offered up only a miserly seven free points, really just had to stay calm and wait for her opponent to self-destruct and Ostapenko fell into the trap.

“I was expecting that she is playing like she played from the beginning: really hard, pushing me back,” Kerber said.

“I was trying to stay focused and play every single point because she started really well. Then I was just trying to find my rhythm and take my chances when I had them.”

Former world number one Kerber needed only 68 minutes to reach her fourth Grand Slam final in which she will face seven-times champion Serena Williams, who beat her in the 2016 final.

Williams dispatched Kerber’s compatriot Julia Georges in straight sets with another show of force.

Kerber can expect less charity in Saturday’s showpiece.

The first game on Friday, served by Ostapenko, was a snapshot of what was to come and illustrated just why the 21-year-old has become such a “must see” player on the WTA Tour and why watching American great Billie Jean King describes the Latvian’s all-or-nothing style as “so much fun”.

CRAZY SEQUENCE

The old adage of feel your way in to a match and start solidly does not appear to apply to Ostapenko who put together a crazy sequence to start her first Wimbledon semi-final.

Kerber was under pressure straight away on her own serve and the match might have taken a different course if Ostapenko had not blazed a forehand long at 30-30 with the court gaping.

The left-hander had to save a break point, too, at 2-3 — conjuring an ace. But the match turned a game later.

Consecutive Ostapenko backhand errors handed 10th seed Kerber the first break and she proceeded to win seven of the next eight games basically by defending well and serving solidly to move into a 5-1 lead in the second set.

Such is the damage Ostapenko can do when her game clicks that even the biggest leads look fragile and, when she suddenly landed some telling blows to claw back two games, a turnaround did not seem out of the question.

Kerber looked worried and Ostapenko had a point to close to within a game but she dumped a backhand return into net and then coughed up two more errors to hand Kerber victory.

“I know she played a lot of good matches where she came back from a score like that, when she has nothing to lose,” Kerber said. “You never know what happen if it went to 5-4.”

Kerber is now back in a Grand Slam title match for the first time since beating Karolina Pliskova in the 2016 U.S. Open final — having begun that year by stunning Serena Williams in the final of the Australian Open.

After suffering a drastic loss of form in 2017, ending the year ranked outside the top 20, a rejuvenated Kerber is back where she feels she clearly belongs.